An interval exercise, or interval training, refers to an exercise session during which you alternate periods of light- to moderate-intensity activity with bursts of high-intensity activity --- rotating between power-walking and jogging or sprinting, for example. Regardless of your current fitness level, you can incorporate interval training into your routine, boosting the length of high-intensity exertion as tolerated. This approach can not only improve your overall cardiovascular performance and enhance fat burning but also serve as a defense against certain chronic conditions such as type 2 diabetes.
Interval Exercise Guidelines
There is no standard recommendation for the ratio between the time of light or moderate exercise and the time of difficult exercise that should be completed in one session. In fact, varying these durations can help move your body toward a higher level of fitness. Still, the general rule is that the high-intensity phase should be long and exhausting enough to make you feel out of breath --- typically one to four minutes, the "New York Times" noted in 2007. The period of recovery, or lower-intensity exercise, should not last long enough for your pulse to return to its resting rate.
With interval training, your aerobic capacity will likely improve, allowing you to exercise longer or with greater intensity. By incorporating bursts of difficult activity, you will burn more calories in the same period of time. Interval training also boosts your body's ability to burn fat. The "New York Times" referenced study results demonstrating that eight young women burned 36 percent more fat in a continuous hour of cycling using the interval approach than when they maintained one intensity level.
As with many cardiovascular exercise programs, interval training can lower your risk of heart disease by helping to control blood pressure and body weight. Study results published in 2008 in the journal "Cardiology Today" explain that interval training yields even more specific health advantages. The study showed that an interval-training test group showed higher insulin sensitivity and lower blood glucose levels, which both work against the development of type 2 diabetes. The aerobic-interval training group also had an increase of 25 percent in levels of HDL, the "good" cholesterol, while participants from the continuous-moderate-exercise and control groups showed no change in HDL levels.
Precautions and Considerations
Because interval training is not appropriate for everyone, consult your physician before beginning a program. Such intensive exercise might not be suitable for those with existing heart disease or stroke risks. Overexertion and stress-related injuries are also possibilities, so do not rush into a strenuous workout, and be cognizant of signs of exhaustion and dehydration. Begin slowly by trying only one or two higher-intensity intervals per session.